Scratch bit



May 30, 1944 J. F. MCQUILLAN, SR 2,350,055

Patented May 30, 1944 UNITED STATES vPA'TEIWF OFFlCi SCRATCH Brr John F.McQuillan, Sr., East Orange, N. J.

Application March 12, 1942, Serial No. 434,422

2 Claims.

This invention relates to an improved scratch bit or blade for use withheighth gauges, planer gauges, and gauge blocks.

The scratch bits now in use with the above mentioned types ofinstruments are provided with a single beveled top surface whichintersects with the bottom surface to form the scratching edge. As aresult, the groove formed by the scratching edge in a piece of work hasa substantially flat lower side and an inclined upper side. This resultsin a definite tendency of the scratch bit to rise or climb While inoperation from .001 inch to .002 inch above the desired height. As thescratch bit is used with measuring instruments intended for extremeaccuracy this variation is very undesirable.

It is, therefore, a primary aim of the present invention to provide ascratch bit having a beveled scratching edge to produce a substantiallyV-shaped groove in the work and to thus produce a bit which will have notendency toward climbing or. rising.

Still a further aim of the invention is to provide `a scratch bit havinga flat bottom surface which is adapted to rest in a suitable support andwhich is adapted to be disposed at the level at which the scratch is tobe made, and having a beveledscratching edge which is disposed inthesame plane as said bottom surface.

Still a further aim of the invention is to provide a beveled cuttingedge disposed in the same plane as the bottom surface of the scratchbit.

`Still another aim of the invention is to provide a scratch bit whereinthe beveled surfaces forming the scratching edge are each disposed at.the same angle to the bottom surface of the bit.

Other objects and advantages of the invention will hereinafter becomemore fully apparent from the following description of the drawings,which illustrate preferred embodiments thereof, and wherein:

Figure 1 is a side elevational view showing one form of the scratch bitattached to a conventional planer gauge,

Figure 2 is a top plan view of the same,

Figure 3 is a side elevational view showing the same form of the scratchbit applied to a gauge block,

Figure 4 is a vertical sectional View taken substantially along theplane of the line 4-4 of Figure 3,

Figure 5 is a longitudinal, substantially central vertical sectionalview of the scratch bit shown in Figures 1 to 4,

Figure 6 is a fragmentary side elevational view showing a slightlymodified form of the scratch bit applied to a height gauge,

Figure is a fragmentary top plan View of the same, and Figure 8 is aperspective view of the scratch bit shown in Figures 6 and 7.

Referring more particularly to the drawings, wherein like referencecharacters designate like or corresponding parts throughout thedifferent views, and referring particularly to Figures 1 and 2, for thepurpose of illustrating one application of the invention, a supportingsurface which is flat is indicated at i9. II designates a piece of worksuch as a forging, casting or steel shape, on a side of which thescratch is to be made and which has one edge resting on the supportingsurface I0. I2 designates generally a conventional planer gauge ofcommon construction and as this instrument forms no part of theinvention a detailed description thereof Ais considered unnecessary.

The scratcher bit, designated generally I3, and comprising the inventionconstitutes an elongated bar of hardened steel or the like which isprovided with a flat bottom surface I4 and a substantially flat topsurface I5 which surfaces are disposed parallel. The bit I3 is providedwith a beveled upper surface I6 at one end thereof which is inclinedtoward andk merges with one end of the top surface I5. The bit I3,

beneath the surface? I6, is provided with an' elongated, dependingportion or projection I1,

forming an integral part thereof, and which depends below the bottomsurface I4. The projection I'I at its outer end is provided with anupwardly and outwardly inclined surface I8 which intersects the surfaceI6 to form the scratching edge I9 of the bit I3. The scratching edge I9is disposed in the same plane as the bottom surface I4 and the beveledsurfaces IB and I8 are each disposed at an angle of 30 degrees to thebottom surface I4 so that the included angle of the scratching edge I9is 60 degrees. The scratching bit I3 is provided with a perpendicularopening or bore 20 which extends therethrough.

In Figures 1 and 2 the scratch bit I3 is shown with its flat undersurface I4 resting on the at top surface of the movable block 2| of theplaner gauge I2. A bolt 22 extends downwardly through the opening 20 andis in threaded engagement with the recess 23 in the block 2| forsecuring the bit I3 to the top surface of the block 2I in a,conventional manner. The elevation of the bit I3 can be adjusted toone-thousandth of an inch by adjustably positioning the block 2|relatively to the inclined channel surface 24 of the base portion of theplaner gauge I2, in a conventional manner. It will thus be readilyapparent that when the block 2| is set at the correct elevation 'theedge I9 will be in the same plane as the top surface of the block 2| andthe under side I4 of the bit I3 so that by relative movement of the bitI3 and the piece of Work II a scratch 25 will be made in the side of theWork II which scratch will be parallel to the bottom edge of the WorkII. Scratch 25 will be V-shaped in cross section, and as previouslyexplained, the shape of the cutting edge I9 will prevent the bit fromrising or climbing While the scratch is being made so that the scratchat all points will be in` the same horizontal plane.

In Figures 3 and 4 the same scratch bit I3 is shown applied to andemployed with a conventional gauge block. This use of the scratch bit I3has the work I I shown supported by the member 26 which is secured tothe surface III by a clamp 2l. The gauge block, designated generally 28,and which is of conventional construction, includes a base 2S havingthreaded openings, not shown. Base 29 rests on and is adapted to be slidrelatively to the surface III and has its top surface disposed at thesame height as the top surface of the portion 30 Which supports thebottom end of the piece of work II. Individual gauge blocks 3| of thedesired sizes rest one upon the other upon the base 29 and the bottomsurface I4 of the bit I3 rests on the upper side of the upper gaugeblock 3I for supporting the bit I3 at any desired elevation to .0001 ofan inch. Another block 32 rests on the base 29 and extends tosubstantially the level of the upper surface I5. A hold-down bar 33extends across the surface I and the top surface of the block 32 and hasa slot therein through which extends a bolt 34, the lower edge of whichis in threaded engagement with one of the threaded openings of thebase-28 for drawing the hold-down bar 33 tight against the upper surfaceof the bit I3l for holding the bit secure1yin place. It will thus beseen that the gauge block 38 can be slid over the surface I to'cause thescratching edge I9 to make a horizontal scratch in the Work II at theexact level of the under side I4 of the bit.

A conventional height gauge 35 is shown in Figure 6 having a supportingarm 36 provided with a clamp 37. The supporting arm 36 is adjustable bymeans 38 relatively to the upright supporting standard 39 Which isprovided with scale markings 4U for adjusting the supporting arm 36 tofractions of one-thousandth of an inch. With the heighth gauge 35 aslightly modified plane surface form of bit, designated I 3', isemployed instead of the bit I3. Bit I3 differs from the bit I3 only inthat it is narrower and not provided with an opening or bore 20. The bitI3 is positioned in the sleeve portion 4I of the clamp 31 and with itsbottom surface I4 resting on the top, at surface of the supporting arm36. A set screw 42 of the clamp 37 is tightened against the top surfaceI5 of the scratch bit I 3' to hold the bottom surface I4 securelyagainst the top surface of the arm 3S. zWhen thus positioned, it will bereadily apparent that the scratching edge of the bit I3 will be in thesame horizontal plane as the upper surface of the supporting arm 36. Thework II is shown resting on the surface I II and against a backingmember 43 and it Will be readily apparent that by moving the heightgauge 35, by sliding its base over the surface I0, that the scratchingedge I9 will make a scratch in the exposed side of the Work II all partsof which scratch will be in a horizontal plane and at the level of theupper side of the supporting arm 35, which is the level at which theheight gauge 35 is set.

Various other modifications and changes in the embodiments of the bits,constituting the invention, are contemplatedand may obviously be resoited to, provided they fall within the spirit and scope of the inventionas hereinafter dened by the appended claims, as only preferredembodiments thereof have been disclosed.

I claim as my invention:

l. A scratch bit for use with height gauges, planer gauges, and gaugeblocks, said bitvhaving a flat bottom surface, said bit having a beveledupper plane surface at one end thereof, a depending projeetion on thebit disposed at said end thereof and extending downwardly from thebottom surface, said projection having a beveled at its cuter end, andsaid beveled surfaces intersecting to form a scratching edge, saidscratching edge being disposed in the same plane as the bottom surfaceof the bit.

2. A scratch bit for use with height. gauges,

i planer gauges, and gauge blocks, said bit having a flat bottomsurface, said bit having a beveled upper plane surface at one endthereof, a depending projection on the bit disposed at said end thereofand extending downwardly from the bottom surface, such projection havinga beveled plane surface at its outer end, and said beveled surfaces eachbeing disposed at the same angle tothe bottom surface and intersectingto form a scratching edge in the same plane as the bottom surface of thebit.. v JOHN F. MCQUILLAN, SR.

